The role of fluoride in the remineralization of carious lesions is well known. The use of agents to enhance this benefit is also well known. One such agent is strontium.
While strontium's inclusion in oral compositions containing fluoride is desirable the agents form an insoluble precipitate unless separated before use or the strontium ions are complexed so as not to be available to form the precipitate. Strontium complexed with ethylene diaminetetraacetic acid (EDTA) is such a complex.
The effect of a strontium-EDTA complex in combination with sodium recinoleate and a fluoride source is found in the Journal of Dental Research (1982) 61 (3) 451-455. The combined effect of strontium and fluoride in reducing the acid solubility of enamel is also disclosed in the Journal of Dental Research (1983) 62 (10) 1049-1053. A further reference discussing the effect of strontium and fluoride is Featherstone, J.D.B. "Remineralization of Artificial Carious Lesions In-vivo and In-vitro", Proceedings Workshop (1983) IRL Press Ltd.
The use of strontium in combination with fluoride in oral compositions is also disclosed in a number of patent references. Included among these references are U.S. Pat. No. 3,888,976, June 10, 1975 to Mlkvys disclosing an effervescent mouthwash tablet containing strontium ions and possibly a fluoride ion source. U.S. Pat. No. 4,367,219, Jan. 4, 1983 to Schole discloses dentifrices containing a combination of strontium EDTA, a recinoleate salt and a fluoride ion source. U.S. Pat. No. 4,415,549, Nov. 15, 1983 to Shah et al. discloses toothpastes containing a glycyrrhizinate salt, strontium EDTA and a fluoride ion source. Finally European patent application no. 0.079,611, June 6, 1983, Shah, discloses oral compositions containing a strontium EDTA complex and a fluoride ion source.
Although the prior art discloses complexes of strontium and EDTA, there is still the need for improvements particularly in achieving greater strontium efficiency.
It has been surprisingly found by the present inventors that very low strontium concentrations can provide enhanced fluoride uptake of a degree not predictable by the prior art.
It is an object of the present invention, therefore, to provide compositions having effectiveness against caries using low levels of strontium.
It is a further object of the present invention to provide compositions effective against caries utilizing strontium EDTA as the strontium ion source.
It is still a further object of the present invention to provide an effective method for providing caries protection.
These and other objects will become readily apparent from the detailed description which follows.
All percentages and ratios used herein are by weight unless otherwise specified.